GAU-8/A Pen/Pencil holder

Modeled the business end of the GAU-8/A Autocannon as a pen/pencil holder for a friend.
Pictured is printed at 125mm high. Any less than 110mm will barely even hold a pencil.
Yes, there is no rifling, wanted there to be enough room for fatter sharpies/pens/whatever.
There is even a hole through the center nut for aircraft safety wire.